Finds the next token in a null-terminated byte string pointed to by str. The separator characters are identified by null-terminated byte string pointed to by delim.

This function is designed to be called multiples times to obtain successive tokens from the same string.

If str !=NULL, the call is treated as the first call to strtok for this particular string. The function searches for the first character which is not contained in delim.

If no such character was found, there are no tokens in str at all, and the function returns a null pointer.

If such character was found, is it the beginning of the token. The function then searches from that point on for the first character that is contained in delim.

If no such character was found, str has only one token, and the future calls to strtok will return a null pointer

If such character was found, it is replaced by the null character '\0' and the pointer to the following character is stored in a static location for subsequent invocations.

The function then returns the pointer to the beginning of the token

If str ==NULL, the call is treated as a subsequent calls to strtok: the function continues from where it left in previous invocation. The behavior is the same as if the previously stored pointer is passed as str.